We have sequenced several HAV cDNA clones by the Maxam and Gilbert technique and to date to two large regions of the genome have been determined. A sequence of 3119 bases corresponding to the 5' end of HAV RNA was sequenced. This sequence contains an open reading frame that begins about 750 bases from the 5' terminus and extends 2407 bases which is as far as sequence has been determined. Sequence preceding this major reading frame has nine other potential initiation sites, but the longest peptide that can be translated in this region is only 26 amino acids. This pattern is consistent with the genomic organization of other picornaviruses. The entire sequence of a clone that mapped to the 3' end of HAV RNA was also determined. A poly(A) tract of 15 bases was found at one end of this clone thus orienting the 3' end of the genome. This poly(A) tract is 51 bases downstream from two closely spaced termination codons that are preceded by 1407 bases in an open reading frame that is presumably continuous with that present at the 5' end of the genome. These sequenced regions of the HAV genome have been compared, using computer programs, to analogous regions previously determined for other picornaviruses. In the past year we have sequenced sufficient clones to span 7.0kb of the HAV genome. Moreover, we were able to deduce from this data the putative sequence of VPg, a protein believed to be covalently attached to the 5' end of the genome. In collaboration with Dr. Maloy, we synthesized a peptide corresponding to the carboxy end of this protein and were able to obtain antisera that immunoprecipitated the VPg-RNA genome complex.